323 



artificial Tam. 



matter, and that the yellow precipitate was the eiTential part 



of the bitumens, which was confirmed by refults from amber ; 



Pit-coal treated feveral experiments were tried with various forts of pit-coal, 



manner, ^ rom a 'l which the brown folution was obtained in abundance, 



but thefe which contained little or no bitumen did not yield 



the yellow precipitate. 



i 



Procefs with the Coal. 



100 grains of coal, in each experiment, were digefted in 

 an open matrafs in a fand heat, with an ounce of nitric acid 

 (of thefp. gravity of 1.40) diluted with two ounces of water, 

 which when warm produced effervefcence, and discharged 

 much gas; after two days, a fecond, and fometimes a third 

 ounce of the acid was added, and the digeftion continued for 

 five or fix days, when nearly the whole was dilTolved, except 

 the precipitate which was conftantly feparated. 

 and charcoal. Charcoal was next tried, which dilTolved more readily than 



the pit coal, and left no refiduum. 



The feveral folutions from afphaltum, jet, pit coal, and 

 charcoal, were evaporated to drynefs gradually to prevent 

 burning the refidue, which from all were of a glofly brown 

 fubiiance, of a refinous fracture, and had the following 

 properties. 

 Properties of the j. They were fpeedily diflblved by cold water, or alcohol. 



foSnsf thefC 2 ' Their flavour was aftl in S enL 



3. Expofed to heat, they fwelled much, and gave a bulky 



coal. 



4. Their folutions in water reddened litmus paper. 



5. And gave copioufly precipitates from muriate of tin, 

 acetite of lead, oxy-fulphate of iron, of a brown colour, 

 except the tin, which was dark grey. 



6. They precipated gold in the metallic Hate from its 

 folution. v* 



7. They alfo precipitated the nitrates of lime, and of 

 barytes, and other earthy lalts. 



8. The fixed alkalis, and ammonia added at firft, deepened 

 their colour, and afterwards made them turbid. 



9. They cau fed precipitates from glue or ifinglafs folutions 

 in water, more or lefs brown according to their ftrenglh, 

 whufh were foluble in cold and boiling water, fo that in their 



eflential 



